CO2-Footprints for Food of Animal Origin - Present Stage and Open Questions

The environmental assessment of human activities is presently a hot topic. It is not only important from an ecological perspective, but also from the view of efficient utilization of limited natural resources such as fuel, land area, water und phosphorus. The environmental impact of food of animal origin is currently quantified by so-called CO2eq-footprints. To define CO2eq-footprints, emissions arising along the food chain will be calculated according to their greenhouse potentials (carbon dioxide = 1 eq; methane a parts per thousand 23 eq, laughing gas a parts per thousand 300 eq). For the primary production of milk, meat and eggs, emissions during crop production, transportation, the storing and processing of feeds, animal keeping, enteric losses and excrement management can be mentioned as examples. Data for CO2eq-footprints in literature for beef and pork/poultry meat presently vary between 7-30 and 2-7 CO2eq/kg empty body weight, respectively. Currently there are different gaps which must urgently be closed before CO2eq-footprints can be specified correctly: Uniform reference basis (e.g. edible fraction or edible protein of animal origin), Clear definition of system borders, Standardisation of methods, further quantification of emissions along the food chain (esp. N2O, but also CH4 and CO2), Improvement of knowledge to reduce emissions along the food chain; consequences of modern biotechnology. At the present stage of knowledge, the ranking of food of animal origin and the introduction of CO2eq-taxes on the basis of CO2eq-footprints may lead to preliminary and possibly wrong conclusions for policy- and decision-makers. Furthermore, interdisciplinary cooperation between scientists working along the food chain is necessary to solve the problems and to develop better and more reliable CO2eq-footprints.